Personally, I'd just cross it over at 80Hz. I had a VMPS RM30C, which is spec'ed pretty low, but still ran it at 80HZ. I think having a sub produce the 80 and below lessens what the center has to do.
I recommend trying both full range and other settings (such as 80Hz), though, to see what you like. The opening to The Fellowship of the Ring is good for this, as is the lobby shooting scene in the Matrix.